Etalon-type variable spectroscopy elements in which two optical substrates provided with optical coating layers on the opposing surfaces face each other and in which the distance therebetween is changeable have been known (for example, refer to Patent Document 1).
This variable spectroscopy element includes sensor electrodes of electrostatic capacitance sensors disposed on the opposing surfaces of the two optical substrates and is capable of detecting the distance between the optical substrates using the electrostatic capacitance sensor and controlling the distance therebetween while maintaining parallelism.
In the variable spectroscopy element in Patent Document 1, level differences are provided on outer peripheral parts of the optical substrates where the sensor electrodes, which connect wires, are provided in order to secure sufficient space for the wires that connect to the sensor electrodes to enable functioning of the electrostatic capacitance sensors; and the outer peripheral parts of the opposing optical substrates are cut away so that interference between the wires or between the wires and the optical substrates is avoided.
Patent Document 1: Japanese Unexamined Patent Application, Publication Number. 2002-277758.